1. Field of the Invention
Exemplary embodiments of the present invention relate to a method for authenticating a low performance device, and more particularly, to a device authenticating method, in which a low performance device such as a smart meter of a smart grid is authenticated in a matrix operation instead of an exponential operation through a homomorphic hash function (HHF) of a non-square matrix M, so that the amount of operations required for authenticating the device can be reduced and the device can be safely authenticated even without a separate certificate authority.
2. Description of Related Art
A smart grid refers to an intelligent power grid which optimizes efficiency of energy by incorporating information technology (IT) into a conventional unidirectional power grid composed of stages of ‘generation of power—transmission of power—distribution of power—sales of power’ and bi-directionally exchanging real-time information between power suppliers and power consumers. The basic concept of the smart grid is to interconnect power plants, power transmission and distribution facilities, and power consumers through an information communication network, and efficiently operate the entire power grid system as one body through information shared bi-directionally.
A power supplier may grasp a power usage state in real-time and flexibly control the amount of power supply using the smart grid, and a power consumer may grasp a power usage state in real-time and control the time and amount of power use by avoiding time zones of high rates based on the power usage state.
The configuration of such a smart grid system will be described hereinafter in further detail with reference to FIGS. 1 and 2.
A management server 10 and a plurality of unit measurement groups 30 are connected to an external network 20. Herein, the management server 10 is a server which receives information on power consumption measured from a unit measurement object such as a house, a building, a factory or the like in real-time and performs a billing process for the consumed power, or transmits power rates changing in real-time to the unit measurement object so that the unit measurement object may efficiently manage electricity based on the power rates. Meanwhile, the unit measurement group is a group that manages power consumption of the unit measurement object existing in an artificially set unit measurement area. The unit measurement group will be described in further detail with reference to FIG. 2. The unit measurement group 30 includes a plurality of measurement devices 31 connected to a data collection unit 35 through an internal network 33. The measurement device 31 measures information on the power consumed by the unit measurement object, and transmits information on the measured power consumption to the data collection unit 35 through the internal network 33 such as a power line communication (PLC), a Zigbee or the like, or receives power management information from the management server 10 through the external network 20 and the internal network 33.
Such a smart grid system performs end-to-end communications between the management server and the measurement device and transmits/receives commercial information such as information on power consumption, power rates and the like in real-time, and thus authentication between the management server and the measurement device and perfect security for the information transmitted and received between the management server and the measurement device are required.
A method for authenticating a device can be largely divided into a public key-based method and a symmetric key-based method. The symmetric key-based method has an advantage in that two devices are provided with a common symmetric key to authenticate each other based on the common symmetric key so that the amount of calculation needed for authentication is small. However, such a symmetric key-based method entails a problem in that the common symmetric key can be comparatively easily exposed to an unqualified third party, and thus if the common symmetric key is exposed to the third party, safe communication is not guaranteed.
On the other hand, in the case of public key-based method, devices performing authentication share a secret key unique to each device. The public key-based method entails a problem in that a device can be authenticated with high reliability using the secret key unique to the device, but an exponential operation is used in the authentication process, so that the method is difficult to implement in a low performance device, and needs a separate certificate authority.
In an attempt to solve the problems associated with the symmetric key- and public key-based authentication methods, an authentication method based on electronic signature between a smart meter and a management server is disclosed in Korean Patent Laid-Open Publication No. 2011-0019506 (hereinafter, referred to as “prior art 1”). For this authentication method, the smart meter has a security authentication module, and the security authentication module should store a pair of public keys for signature. Public key processing based on exponential operations can be performed without a problem since the management server is of high performance. However, since the smart meter is an embedded system having a relatively low operating capability, a high-performance security authentication module capable of performing electronic signature is used in the smart meter in order to solve this problem. However, prior technology 1 is difficult to be used in a smart grid system which uses low performance measurement devices.
In the meantime, Korean Patent Laid-Open Publication No. 2008-96181 (hereinafter, referred to as “prior art 2”) discloses a method capable of authenticating a counterpart measurement device even without a separate certificate authority among a plurality of measurement devices constituting a power line communication network. In the prior art 2, a hash function based on a random number is used for authentication between a management server and a measurement device or between measurement devices, and the management server periodically updates the public key pair instead of not requiring communication with a third party authority. This public key pair is used to secure safety of communications. In relation to prior art 2, a method of authenticating a device according to an RSA encryption scheme involves a problem in that since it is based on complex exponential operations, it is difficult to be used in a smart grid system which uses low performance authentication devices.